Bicycle rear sprocket adapter

Abstract

A bicycle rear sprocket adapter comprises a plurality of external spline teeth and a plurality of internal spline teeth. The plurality of external spline teeth is configured to engage with a bicycle rear sprocket assembly. The plurality of internal spline teeth is configured to engage with a bicycle hub assembly. At least two internal spline teeth of the plurality of internal spline teeth are circumferentially arranged at a first internal pitch angle with respect to a rotational center axis of the bicycle hub assembly. The first internal pitch angle ranges from 10 degrees to 20 degrees.

What is claimed is: 
     
       1. A bicycle rear sprocket adapter comprising:
 a plurality of external spline teeth configured to engage with a bicycle rear sprocket assembly; and 
 a plurality of internal spline teeth configured to engage with a bicycle hub assembly, the plurality of internal spline teeth each comprising an internal-spline driving surface to transmit a driving rotational force to the bicycle hub assembly during pedaling, 
 at least two internal-spline driving surfaces of the internal-spline driving surfaces of the plurality of internal spline teeth being circumferentially arranged at a first internal pitch angle with respect to a rotational center axis of the bicycle hub assembly, the first internal pitch angle ranging from 10 degrees to 20 degrees, 
 at least two internal-spline driving surfaces of the internal-spline driving surfaces of the plurality of internal spline teeth being circumferentially arranged at a second internal pitch angle with respect to the rotational center axis, 
 the second internal pitch angle being different from the first internal pitch angle, 
 the internal-spline driving surfaces each including
 a radially outermost edge, 
 a radially innermost edge, and 
 a radial length defined from the radially outermost edge to the radially innermost edge, 
 
 a total of the radial lengths of the internal-spline driving surfaces being equal to or larger than 7 mm, 
 the plurality of external spline teeth includes
 a plurality of first external spline teeth each having a first circumferential width defined in a circumferential direction with respect to the rotational center axis, and 
 a first additional external spline tooth having a first additional circumferential width defined in the circumferential direction, the first additional circumferential width being different from the first circumferential width, 
 
 the plurality of internal spline teeth includes
 a plurality of first internal spline teeth each having a second circumferential width defined in the circumferential direction, and 
 a first additional internal spline tooth having a second additional circumferential width defined in the circumferential direction, the second additional circumferential width being different from the second circumferential width, and 
 
 the second additional circumferential width is different from the first additional circumferential width. 
 
     
     
       2. The bicycle rear sprocket adapter according to  claim 1 , wherein
 the first internal pitch angle ranges from 12 degrees to 15 degrees. 
 
     
     
       3. The bicycle rear sprocket adapter according to  claim 2 , wherein
 the first internal pitch angle ranges from 13 degrees to 14 degrees. 
 
     
     
       4. The bicycle rear sprocket adapter according to  claim 1 , further comprising
 an indicator to indicate a circumferential position of the bicycle rear sprocket adapter. 
 
     
     
       5. The bicycle rear sprocket adapter according to  claim 4 , further comprising
 an axial end surface, wherein 
 the indicator is provided on the axial end surface. 
 
     
     
       6. The bicycle rear sprocket adapter according to  claim 1 , wherein
 a total number of the plurality of external spline teeth is equal to or smaller than nine. 
 
     
     
       7. The bicycle rear sprocket adapter according to  claim 1 , wherein
 at least one of the plurality of external spline teeth having an external-spline major diameter larger than 34 mm and smaller than 35 mm. 
 
     
     
       8. The bicycle rear sprocket adapter according to  claim 1 , wherein
 the plurality of external spline teeth is circumferentially arranged at an external pitch angle with respect to the rotational center axis. 
 
     
     
       9. A bicycle rear sprocket adapter comprising:
 a plurality of external spline teeth configured to engage with a bicycle rear sprocket assembly; and 
 a plurality of internal spline teeth configured to engage with a bicycle hub assembly, the plurality of internal spline teeth having an internal-spline minor diameter equal to or smaller than 30 mm, the plurality of internal spline teeth each comprising an internal-spline driving surface to transmit a driving rotational force to the bicycle hub assembly during pedaling, 
 at least two internal-spline driving surfaces of the internal-spline driving surfaces of the plurality of internal spline teeth being circumferentially arranged at a first internal pitch angle with respect to a rotational center axis of the bicycle hub assembly, 
 at least two internal-spline driving surfaces of the internal-spline driving surfaces of the plurality of internal spline teeth being circumferentially arranged at a second internal pitch angle with respect to the rotational center axis, 
 the second internal pitch angle being different from the first internal pitch angle, 
 the internal-spline driving surfaces each including
 a radially outermost edge, 
 a radially innermost edge, and 
 a radial length defined from the radially outermost edge to the radially innermost edge, 
 
 a total of the radial lengths of the internal-spline driving surfaces being equal to or larger than 7 mm, 
 the plurality of external spline teeth includes
 a plurality of first external spline teeth each having a first circumferential width defined in a circumferential direction with respect to the rotational center axis, and 
 a first additional external spline tooth having a first additional circumferential width defined in the circumferential direction, the first additional circumferential width being different from the first circumferential width, 
 
 the plurality of internal spline teeth includes
 a plurality of first internal spline teeth each having a second circumferential width defined in the circumferential direction, and 
 a first additional internal spline tooth having a second additional circumferential width defined in the circumferential direction, the second additional circumferential width being different from the second circumferential width, and 
 
 the second additional circumferential width is different from the first additional circumferential width. 
 
     
     
       10. The bicycle rear sprocket adapter according to  claim 9 , wherein
 the internal-spline minor diameter is equal to or larger than 25 mm. 
 
     
     
       11. The bicycle rear sprocket adapter according to  claim 10 , wherein
 the internal-spline minor diameter is equal to or larger than 29 mm. 
 
     
     
       12. The bicycle rear sprocket adapter according to  claim 9 , wherein
 the plurality of internal spline teeth has an internal-spline major diameter equal to or smaller than 28 mm. 
 
     
     
       13. The bicycle rear sprocket adapter according to  claim 12 , wherein
 the internal-spline major diameter is equal to or larger than 25 mm. 
 
     
     
       14. The bicycle rear sprocket adapter according to  claim 13 , wherein
 the internal-spline major diameter is equal to or larger than 27 mm. 
 
     
     
       15. The bicycle rear sprocket adapter according to  claim 9 , wherein
 the total of the radial lengths is equal to or larger than 10 mm. 
 
     
     
       16. The bicycle rear sprocket adapter according to  claim 9 , wherein
 the total of the radial lengths is equal to or larger than 15 mm. 
 
     
     
       17. A bicycle rear sprocket adapter comprising:
 a plurality of external spline teeth configured to engage with a bicycle rear sprocket assembly; and 
 a plurality of internal spline teeth configured to engage with a bicycle hub assembly, the plurality of internal spline teeth each comprising:
 an internal-spline driving surface to transmit a driving rotational force to the bicycle hub assembly during pedaling, the internal-spline driving surface having a first internal-spline-surface angle defined between the internal-spline driving surface and a first radial line extending from a rotational center axis of the bicycle rear sprocket adapter to a radially outermost edge of the internal-spline driving surface; and 
 an internal-spline non-driving surface having a second internal-spline-surface angle defined between the internal-spline non-driving surface and a second radial line extending from the rotational center axis of the sprocket adapter to a radially outermost edge of the internal-spline non-driving surface, the second internal-spline-surface angle being different from the first internal-spline-surface angle, 
 
 at least two internal-spline driving surfaces of the internal-spline driving surfaces of the plurality of internal spline teeth being circumferentially arranged at a first internal pitch angle with respect to the rotational center axis, 
 at least two internal-spline driving surfaces of the internal-spline driving surfaces of the plurality of internal spline teeth being circumferentially arranged at a second internal pitch angle with respect to the rotational center axis, 
 the second internal pitch angle being different from the first internal pitch angle, 
 the internal-spline driving surfaces each including
 a radially outermost edge, 
 a radially innermost edge, and 
 a radial length defined from the radially outermost edge to the radially innermost edge, 
 
 a total of the radial lengths of the internal-spline driving surfaces being equal to or larger than 7 mm, 
 the plurality of external spline teeth includes
 a plurality of first external spline teeth each having a first circumferential width defined in a circumferential direction with respect to the rotational center axis, and 
 a first additional external spline tooth having a first additional circumferential width defined in the circumferential direction, the first additional circumferential width being different from the first circumferential width, 
 
 the plurality of internal spline teeth includes
 a plurality of first internal spline teeth each having a second circumferential width defined in the circumferential direction, and 
 a first additional internal spline tooth having a second additional circumferential width defined in the circumferential direction, the second additional circumferential width being different from the second circumferential width, and 
 
 the second additional circumferential width is different from the first additional circumferential width. 
 
     
     
       18. The bicycle rear sprocket adapter according to  claim 17 , wherein
 the first internal-spline-surface angle is smaller than the second internal-spline-surface angle. 
 
     
     
       19. The bicycle rear sprocket adapter according to  claim 17 , wherein
 the first internal-spline-surface angle ranges from 0 degree to 10 degrees. 
 
     
     
       20. The bicycle rear sprocket adapter according to  claim 17 , wherein
 the second internal-spline-surface angle ranges from 0 degree to 60 degrees.